1. The Field of the Invention
The present invention is related to thermosetting plastic compositions made with comminuted recycled glass particles and powder as a filler and reinforcement.
2. The Background of the Invention
Thermosetting plastics are commercially accepted as protective and decorative coatings for surfaces made of a variety of materials, including steel, aluminum, wood, and concrete. The basic thermosetting plastic composition is made of a thermosetting plastic resin and a hardener. As used herein, the term thermosetting plastic resin is intended to include both the resin and the hardener. Epoxy and phenolic plastic resins are common thermosetting plastic resins that can be used to produce these thermosetting plastic compositions.
Although pure thermosetting plastic compositions protect surfaces, a variety of aggregates are commonly added to the thermosetting plastic resin to modify the plastic""s characteristics. For example, it is common to add coloring agents to epoxy resin for decorative purposes. Other aggregates are commonly added to thermosetting plastics to alter mechanical properties such as the resistance to impact and abrasion, the tensile and compressive strength, and the resistance to various chemicals and chemical reactions. As used herein, a plastic xe2x80x9cfillerxe2x80x9d is an ingredient which has a cost substantially less than the cost of the plastic used. As used herein, a plastic xe2x80x9creinforcementxe2x80x9d is an ingredient which is included in the plastic to provide a desired property or characteristic.
Specially manufactured glass has been used as an ingredient in thermosetting plastics. For instance, commercially available glass fibers or whiskers, having a length of about xc2xc inch, have been added to plastic to make the product tougher and to improve the yield stress. Manufactured glass beads (either solid or hollow) have also been used in thermosetting plastics to improve to toughness and abrasion resistance of the plastic. However, the manufactured glass fibers and beads cost approximately the same as the plastic used. The manufactured glass fibers and beads have been used solely to provide desired mechanical properties in the finished plastic product. They have not been used as a filler in plastic to reduce manufacturing costs.
One commercially successful thermosetting composition uses silica sand as an ingredient in thermosetting plastics used as a protective coating on floors or other surfaces exposed to excessive wear. In this commercially successful application, the silica sand is mixed with the thermosetting plastic resin and then a thin layer of the resulting composition is applied to the surface. The layer is then allowed to cure, or harden. The desired protection is typically obtained by applying multiple layers of the thermosetting plastic and silica sand composition. Before applying each additional layer, silica sand is spread over the previous layer while it is curing. The silica sand becomes affixed in the thermosetting plastic as it cures. The surface of the previous layer is then sanded in preparation for application of the additional layer of thermosetting plastic and silica sand composition.
The benefits that silica sand provides to thermosetting plastics come at considerable expense. The Material Safety Data Sheet for silica sand, also known as crystalline silica, identifies several potential health effects presented by inhalation of silica sand dust. Respirable crystilline silica is produced in many circumstances, such as, for example, sandblasting, concrete cutting, mining, and mixing sand with cement. Essentially anything that can disrupt the crystalline structure of the silica sand may produce respirable crystalline silica. Silicosis is a known, chronic, adverse health effect from regular exposure to respirable crystalline silica. Silicosis results in a fibrosis of the lungs that is often progressive leading to disability and death. Additionally, silicosis increases the risk of tuberculosis. These known health risks have caused the Office of Occupational Health and Safety to set a low permissible exposure level (PEL) for crystalline silica of 10 mg/m3. In addition to the risks of silicosis and tuberculosis, studies have shown that crystalline silica is a carcinogen and that workers exposed to respirable crystalline silica have an increased risk of developing connective tissue disorders, chronic kidney disease, and end-stage renal disease. These additional studies have caused several agencies to established recommended exposure levels as low as 0.05 mg/m3.
Common methods of forming protective coatings from thermosetting plastic with silica sand produce several opportunities for respirable crystalline silica to be released into the air near workers applying the coating. For example, crystalline silica dust is released when the silica sand is added to the thermosetting plastic resin. Additionally, respirable crystalline silica is released into the air when the silica sand is spread over the curing layer of epoxy in preparation for additional layers. Moreover, the worker sanding the cured epoxy layer coated with silica sand will create respirable crystalline silica in the sanding area. An employee working on any of these steps would be exposed to respirable crystalline silica and incur increased risks of the adverse health effects discussed above.
Executive Order 13101, entitled Greening the Government Through Waste Prevention, Recycling, and Federal Acquisition, recently defined the federal government""s position towards recycling and the use of natural resources. That order declared that xe2x80x9cit is the national policy to prefer pollution preventionxe2x80x9d and recycling. Consistent with that policy, the order directed each of the executive agencies to develop a plan for increasing the acquisition of recycled products and environmentally preferable products. The Executive Order itself does not set any specific requirements on the agencies but does require the Environmental Protection Agency (EPA) to regularly update a list of xe2x80x9citems that are or can be made with recovered material.xe2x80x9d Furthermore, the Order requires that agencies modify their procurement programs to prefer purchasing an item containing recovered materials once the EPA has identified the item. Several other requirements in the Executive Order illustrate the strength of the federal government""s commitment to reducing waste through promoting and favoring recycling.
Therefore, it would be an improvement in the state of the art to provide a thermosetting plastic that is reinforced with a low-cost filler material to further reduce manufacturing costs. Furthermore, it would be an advancement in the art to provide a reinforced thermosetting plastic with a filler ingredient that does not present health risks to those making or using the plastic. Additionally, it would be an improvement in the art to provide a reinforced thermosetting plastic whose filler ingredient comprises a recycled material that is inexpensively produced and furthers the national policy in favor of recycling. Such a thermosetting plastic composition and methods of applying the same to protect surfaces are described herein.
The present invention is directed towards a thermosetting plastic composition comprising uncontaminated, comminuted, recycled glass powder filler having non-uniform, rounded edges which has been comminuted without the use of grinding compounds and thermosetting plastic resin. The composition comprises up to 80% by weight comminuted glass powder filler. As used herein, the term xe2x80x9cglass powderxe2x80x9d refers to powders or particles smaller than about 8 mesh. The glass powder filler has a size less than about 8 mesh, preferably ranging from about 20 mesh to about 30 mesh. The glass powder filler may be as small as about 100 mesh or smaller. Preferably, the thermosetting plastic composition comprises between about 30% and about 80% by weight comminuted glass powder filler.
The present invention is also directed towards a kit for producing a thermosetting plastic coating. The kit comprises uncontaminated, comminuted, recycled glass powder filler having non-uniform, rounded edges which has been comminuted without the use of grinding compounds and a thermosetting plastic resin. The thermosetting plastic coating is formed when the uncontaminated glass powder filler and the thermosetting plastic resin are combined. The comminuted, recycled glass powder filler has a size less than about 8 mesh, preferably ranging from about 20 mesh to about 30 mesh. The glass powder may be as small as about 100 mesh or smaller. The coating comprises up to about 80% by weight comminuted glass powder filler, preferably the coating comprises between about 30% and about 80% comminuted glass powder filler.
Additionally, the present invention is directed to a method of protecting a surface with a thermosetting plastic coating. The method comprises the steps of obtaining a quantity of uncontaminated, comminuted, recycled glass powder filler having non-uniform, rounded edges which has been comminuted without the use of grinding compounds, combining the comminuted glass powder filler with a quantity of thermosetting plastic resin to form a thermosetting plastic composition, and coating a surface with the composition. The composition comprises up to about 80% by weight comminuted glass powder filler and preferably between about 30% and 80% by weight comminuted glass powder filler. The comminuted glass powder filler in the composition has a size less than about 8 mesh, preferably the glass powder has a size ranging from about 20 mesh to about 30 mesh. The glass powder may be as small as about 100 mesh or smaller. The coating step may be performed with an applicator such as a brush, roller, trowel, or similar spreader. The coating step may be performed so that the resulting thermosetting plastic layer on the surface ranges from about xe2x85x9 inch thick to about xc2xd inch thick. Preferably, the resulting thermosetting plastic layer is about xc2xc inch thick.